Injector type indirect evaporative condensers

ABSTRACT

An indirect evaporative heat exchanger such as a condenser operating on the injection or aspiration principle in which the air is pumped solely by the injection of water which also serves to maintain wet the surface of the tubes of the condenser.

United States Patent 1 1 Engalitcheff, Jr. 1 Apr. 2, 1974 [5 INJECTORTYPE INDIRECT 1,914,032 6/1933 Mackan 62 314 x EVAPORATIVE CONDENSERS1,929,583 10/1933 Halsey 62/314 2,088,962 11/1937 Kleuckcr.. 62/314 XInventor: J Engalilcheff, J Glbson 2,152,251 3 1939 Gay 62 314 x Island,Md. 2,217,130 10/1940 Nichart.... 261/152 X 2,270,546 1/1942 Nculand...417/179 X 173] Assgnw Balt'more Company 2,919,559 1 1960 KOCh 62 314 xJCSSUP, 2,933,904 4 1960 Wellman 62 305 1 FilcdI May 19, 1971 FOREIGNPATENTS OR APPLICATIONS [21] Appl. N0.: 144,854 1,028,041 5/19'66 GreatBritain 417 179 Primary Examiner-Albert W. Davis, Jr. [52] US. Cl62/310, 62/305, 62/314,

261/152, 417/179, 417/198 Attorney, Agent, or Firm Michael C. Sudol, Jr.[51] Int. Cl. ..-F28d 5/00 58 Field 61 Search 62/305, 314, 310; 261/152,[57] ABSTRACT 2 1 11 417 179 193 An indirect evaporative heat exchangersuch as a condenser operating on the injection or aspiration princi-[56] References Cited ple in which the air is pumped solely by theinjection UNITED STATES. ATENTS of water which also serves to maintainwet the surface of the tubes of the condenser. 1,151,259 8/1915 Fischer417/198 7 1,373,231 3/1921 Gardner et a1 62/314 X 6 Claims, 8 DrawingFigures 1 OUT 1 62 I AIR IN 2 so 63-" /Y 68 2 SHEEI 1 0f 7 PAIENIED APR2 I974 AIR OUT AIR IN IVIVVENTOR JOHN ENGALITCHEFF, JR.

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INJECTOR TYPE INDIRECT EVAPORATIVE CONDENSERS This invention relates tothe art of evaporative heat exchangers of the indirect type and moreparticularly to an improved evaporative condenser or closed circuitevaporative cooler.

Evaporative heat exchangers of the indirect type are widely used todaywhere it is necessary to cool or to condense a fluid such as arefrigerant which must be maintained out of contactrthat is in indirectheat exchange relationship, with the heat exchange medium to which theheat is transferred. In general the principle of the indirect heatexchange evaporative cooler is that the fluid from which heat is to beextracted is flowed through tubes the exterior surface of which ismaintained wet with water. Air is circulated over the wet tubes topromote evaporation of the water and the heat of vaporization necessaryto support that evaporation of water is supplied from the fluid withinthe tubes thus bringing about the desired heat extraction and/orcondensation. That portion of the cooling water which is not evaporatedis recirculated and, of course, losses by evaporation are made up.

In the conventional evaporative condenser the water is sprayed to flowby gravity over the heat exchange tubes in which the refrigerant iscirculated and air is flowed upwardly through the tubes counter to thewater to promote evaporation. Such a system requires a water pump topump the water to the spray heads and an air blower to pump the air.Both involve cost to construct, both consume power in use and bothrequire maintenance.

It is therefore an object of this invention to provide an evaporativeheat exchange system suitable for cooling or condensation on an indirectheat exchange basis in which the water which wets the external surfaceof the tubes of the system is so supplied as to induce the flow of suchair as is necessary to promote efficient water evaporation, thusreducing the number and complexity of the parts by eliminating the needfor moving parts in the air propulsionsystem with resulting savings incost of construction and maintenance.

Another object of the present invention is to provide an evaporativeheat exchanger of the indirect type characterized by compactconstruction of low profile and quiet operation.

Other objects and advantages of the present invention will be apparentupon consideration of the following detailed description of a preferredembodiment thereof in conjunction with the annexed drawings wherein:

F IG. 1 is a view in vertical section of an evaporative condenserconstructed in accordance with the principles of the present invention;

FIG. 2 is a top plan view of the evaporative condenser of FIG. 1;

FIG. 3 is a view in section taken on the line 33 of FIG. 1;

FIG. 4 is a view in section taken on the line 4-4 of FIG. 1;

FIG. 5 is a fragmentary view of a water supply arrangement involving awater pump having a variable speed drive so that with its use the systemcan be operated below available capacity;

FIG. 6 is a view partially in vertical section and partially inelevation of a horizontal axis type evaporative condenser according tothe present invention;

FIG. 7 is a view in elevation at the inlet end of the apparatus of F IG.6; and

FIG. 8 is a view similar to FIG. 6 but showing two evaporativecondensers arranged one above the other and employing a common sump.

Referring now in greater detail to the drawings, in FIG. 1 theillustrated evaporative condenser is comprised of an injector portion 10and an air venting stack 11. The injector portion has anouter wall 12and an inner wall 13, the latter being common to and constituting theinner wall of stack 11. Stack 11 has an outer wall 14 and, connectingthe outer walls 12 and 14 at opposite ends of the apparatus are commonend walls 15 and 16. The structure defined by the walls l2 -l6,inclusive, has a common bottom sheet 17 which extends the width of theapparatus from wall 12 to wall 14 and the length thereof from wall 15 towall 16.

Walls 12 and 13 are so contoured, see FIGS.- 1 and 2, as to define asort of venturi having a long rectangular mouth 18, a long rectangularthroat l9 narrower than the mouth, and a long rectangular lower region20 wider than the throat 19. Above the mouth 18 there extends lengthwiseof the apparatus a water supply conduit 21. Depending from this conduitare two rows of conduits 22 and 23 each such conduit terminating in anozzle 22n or 23n. The nozzles 2211 and 23n are adapted to spray apattern of water generally oval in cross section with the long axes ofthe adjacent spray patterns generally aligned with each other andparallel to the end walls 15 and 16 of the apparatus, see FIG. 2. Thewater from the rows of nozzles 22n and 23n strikes the inside of thewalls 12 and 13 at or near the region of the throat 19. The sprayinduces air flow into the system at the mouth 18. The theory ofoperation of the injection air pumping system of the present inventionis described in greater detail in applications Ser. No. 826,638, filedMay 21, 1969, and Ser. No. 869,798, filed Oct. 27, 1969, and istherefore not repeated here.

In the path of the water and air flowing downwardly in the injector 10there are located the tubes 24 through which the fluid to be condensedor cooled is circulated. These tubes extend between a header 25 and aheader 26. The fluid to be condensed or cooled is supplied to header 25through a conduit 27 which passes through wall 15, see FIGS. 1, 3 and 4.The fluid flows through the tubes 24 which extend between header 25 andheader 26, enters header 26 and is withdrawn from header 26 through aconduit 28 which also passes through wall 15.

The tubes 24 are arranged in diagonally offset pairs such as tubes 24aand 24b of FIG. 4. The tubes run from the header 25 to the back wall 16and then forward to a position near the front wall 15, then back againto the rear wall 16, and finally forward'to the header 26. Enough pairsof tubes are supplied to traverse the space between the lower end ofwall 13 and the side wall 12. The arrangement of tubes is such as toexpose the full length of each tube to the water spray and the flowingair so that the full length of each tube is kept wet at all times andevaporation is promoted to cool or condense thefluid flowing within thetube. 1

It will be observed that the tubes 24 as a group form a permeablerectangular body of substantially uniform thickness. This body hassubstantially the same length as the distance from wall to wall 16, seeFIG. 2. On the other hand, its width is greater than the width of theregion of the injector 12 at the horizontal plane of the lower end ofthe wall 13. Thus, the tubes 24, as a group, define a permeable body ofuniform thickness so disposed in the apparatus that the plane of thesurface of said body lies at an oblique angle to the long axis of theinjector 12.

As can best be seen in FIGS. 3 and 4, the tubes 24 are physicallysupported from pipes 33 which are supported in L section members 34 and35 attached respectively to walls 16 and 15. The L section members 34and 35 are provided with holes along the length thereof and thesupporting pipes 33 are passed through these walls and through the bendsin the tube and once in position may be welded as indicated at 36. Whenthe run of tubes is a long one, it is also customary to provide aconventional support structure in the middle of the tube bank betweenthe end walls.

The water which issues from the nozzles 22n and 23n and which does notevaporate from the surface of tubes 24 is collected in a sump at thebottom of the apparatus. The sump is provided with a water outlet at 37and strainer screens at 38 and 39. The water is pumped from the sumpthrough outlet 37 to the pipe 21 by a pump, not shown. The water levelis maintained by a float-controlled makeup valve, not shown. Note thatthis level is maintained below the lower extremity of the banks of heatexchange tubes 24. The recirculation I of the water from sump outlet 37to conduit 21 can be metered by any conventional means, such as athrottle valve or a variable capicity pump, see FIG. 5. If the amount ofwater supplied to conduit 21 is reduced, the amount of air pumped isalso reduced and thus there is provided a convenient method for capacitycontrol. In other words, when ambient temperatures are low or when theheat load is low, reduced water flow will throttle down the apparatus tomeet the lower load condition.

In FIG. 5 a pump 40 is shown for delivering water from the outlet 37 ofsump 17 to conduit 21 which serves the spray nozzles. The pump 40 iscapable of operation at variable speeds. It is controlled by a variablespeed motor 41 which can be operated by a temperature sensor measuringthe fluid temperature within the coil or a function thereof.

Heat exchange tubes 24 are so positioned that not only are they kept wetfor efficient operation as coolers or condensers, but they likewise verylargely remove droplets from the water which passes through them.Accordingly, theair which also passes through them as indicated by thearrows in FIG. 1 exhausts to atmosphere through the stack 11substantially free of droplets. lf further removal of droplets isnecessary, a row of mist eliminators 42 may be disposed from the frontwall 15 to the back wall 16 of the apparatus in an angular positionbetween the upper right corner of the tube system and the wall 14approximately at the level of the sump water. These mist eliminatorscorrespond in structure and function to those shown in application Ser.No. 869,798, filed Oct. 27, 1969.

It is to be noted that wall 13 which is common both to the injector l0and the stack 11 is so contoured that it helps define the mouth 18, thethroat 19 and the diffusion portion 20 of the injector while at the sametime defining an air exhaust stack which tapers inwardly so that at theupper, exhaust end 43 thereof the air dircharges at a high velocitywhich assists in preventing exhaust air from recirculating to the airinlet of the system. Recirculation is also inhibited by the fact thatthe mouth 18 of the injector lies in a plane below the plane of theupper end of the stack 11.

It will be appreciated that the heat load in the water, evaporation ofwhich cools the fluid within the heat exchange tubes, is transferred tothe exhausting air. This air therefore contains the heat load in theform oflatent and sometimes sensible heat as well and is nearlysaturated with water. In this condition it can no longer function totake up more heat and more water, and it is for this reason that itsrecirculation must be prevented; for if it were not prevented, drasticreduction in efficiency would result. I

While in FIG. 1 there is shown a single elongated injector with a singlestack, where additional capacity is needed it is entirely feasible toduplicate a mirror image of the apparatus shown in FIG. 1 on theopposite side of the plane of wall 14 in which case, of course, wall 14itself is eliminated.

FIGS. 6 and 7 illustrate an embodiment of the invention in which theinjector acts generally horizontally. There is a casing having an airinlet mouth 50 at one end and an air discharge portal 51 at the otherend. The casing is defined by two vertical side walls 52 and 53 andsloping upper and lower walls 54 and 55. The air inlet 50 is rectangularas can be seen in FIG. 6, the long axis of the inlet being horizontaland the short axis vertical. The upper margin portion 56 of the airinlet 50 is curved to define a bell mouth and this is also true of lowermargin portion 57. The bell mouth portions 56 and 57 lead through aregion of convergence defined Water is sprayed into the throat region 60from a plurality of nozzles 61. As illustrated these nozzles arearranged in four horizontal rows, each having a water supply pipe 62.All of the pipes 62 are fed from a common header 63.

The water issuing from each nozzle forms a spray which is generally ovalin cross section, see FIG. 7. The pipes 62 are so spaced vertically fromone another that the upper and lower edges of each spray intersect justabout at the plane of the throat 60. The nozzles 61 are so spaced inrelation to one another along the respective pipes 62 that the sideedges of the spray just about touch one another at the plane of thethroat, see again FIG. 7.

The theory of operation of these sprays in pumping air in a horizontalsystem is explained in application Ser. No. 144,853 filed May 19, 1971;and is therefore not repeated here.

The water sprays flowing the length of the casing inpinge against a tubebank 64 structurally and functionally similar to tube bank 24 shown inFIGS. 1, 3 and 4. The fluid to have heat extracted from it enters thetube bank 64 through conduit 65 similar in structure and function toconduit 27 of FIG. 1. The fluid leaves the tube bank 64 through conduit66.

Note that the tube bank or coil 64 is tilted at a slight angle whichapproximates the angle of slope of the lower wall 55, see FIG. 6. Thetilt will ensure that the coil is fully wetted across its face andthroughout its depth. In view of the fact that the coil 64 itselffunctions somewhat as a mist eliminator, ordinarily only a by upper andlower walls 58 and 59 to a throat region single bank of mist eliminatorswill be necessary, and these are shown at 67. In cross section thesecorrespond in appearance to FIG. 4 of application Ser. No. 869,798,filed Oct. 27, I969. The air leaving outlet portalSl having passedthrough eliminators 67 is guided by turning vanes 68 which direct theheat and moisture laden air up and away from the inlet mouth 50 to avoidany tendency to recirculation.

It should be noted that in a conventional evaporative condenser fanspump the air and only enough water is pumped to wet the coil surfaces.Using minimum water quantities in this way sometimes results in areas oflight coverage with a tendency to form scale on the tubes. Of course, inan ejector evaporative condenser, the water serves the dual purpose ofboth pumping the air and wetting the coil. The total amount of energyinput for such an ejector is approximately equal to the sum of the pumpand fan motor horsepower ofa conventional type unit. In an ejector theenergy input is measured by the nozzle pressure and water flow quantity.Therefore for an equal amount of energy the amount of water pumped wouldbe much higher than a conventional evaporative condenser. This waterflow would be approximately two to three times as great per square footof the coil cross-sectional area (as viewed from the sprays.) Thisadditional water has the advantage of eliminating any dry spots whichtend to scale and also promotes better heat transfer from the tubes tothe water and then tothe air.

The apparatus'shown in FIGS. 6 and 7 has a spigot 69 for supplyingmakeup water to the sump 70 under the control of a float 71. Waterleaves the sump 70 through a conduit 72. and is delivered by pipes, notshown, back to header 63. A blowdown arrangement is shown in which waterextracted from the lowermost pipe 62 passes through a conduit 73 to oneend of a trough constituting part of the bell mouth 57. Water leaves theother end of this trough through a conduit 74 which discharges through aconvenient connection 75. .The blowdown arrangements, the water supplyarrangements, and the nozzles all are fully described in applicationSer. No. 144,853 filed May 19, I971 and need not be further discussedhere.

Where increased condensing capacity is needed and it is not convenientto achieve that capacity by enlarging units such as are shown in FIGS. 6and 7, it is possible to use multiples of these units arranged one uponthe other. For example, in FIG. 8 there is shown an arrangement whichis, in effect, like the unit of FIG. 6 with another similar unit locatedabove it. In FIG. 8 the water'supply, the pumping of the air, thepositioning of the tubes, the structure and positioning of the misteliminators, and of the turning vanes is the same as is shown in FIG. 6.These parts are therefore given the same numbers which they had in FIG.6. The upper unit 80 of FIG. 8, however, does have a sump of its owndifferent in structure from the sump 70. This sump 81 drains waterthrough the tubes 64 of the lower evaporative condenser unit 82 to thesump 70. Except for this difference and the fact that the drain 83underneath the nozzles 61 of the upper unit 80 is connected by a pipe 84to the basin 81' from which it drains also through the tubes 64 of thelower unit 82 into the sump 70, these units are identical.

While the apparatus of the present invention has been described inconjunction with an evaporative condenser, it is to be understood thatany type of cooling or condensing that requires the fluid from whichheat is to be extracted to be maintained out of Contact with the mediumwhich extracts the heat is within the intended use of the apparatus. Theterm indirect heat exchange as used herein is to express the situationwhere a fluid from which heat is to be extracted is physically isolated(as by tubing) from contact with the medium (such as water) to which theheat is transferred. This term is used to distinguish from direct heatexchange as in a cooling tower where the water from which heat isextracted is in direct contact with the evaporating water to which theheat is transferred.

While the illustrated apparatus discloses four coil passes between theinput and output headers, it is to be understood that the number of coilpasses can be varied as necessary to meet the capacity requirements ofthe system.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics hereof. The embodiment andthe modification described are therefore to be considered in allrespects as illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed. is:

1. An evaporative heat exchanger of the indirect type comprising meansdefining a conduit extending in a horizontal direction and having an airintake at one end exposed to the ambient, means to inject water in ahorizontal direction within the conduit in the form ofa plurality ofsprays of sufficient divergence to contact the inner surface of theconduit and to inersect each other within the conduit, thereby to pumpambient air into the conduit at its intake end, enclosed means toreceive. the water issuing from the other end of said conduit, means topump the water from said water receiving means to said injecting means,a tube bank positioned in said conduit, said tube bank comprising aplurality of tubes arranged in diagonally offset pairs which traversethe space between the walls of the conduit thereby to form a permeablebody, said tube bank being positioned in the path of said water betweensaid common plane and said water receiving means, to be impinged upon bysaid water sprays, said tubes being arranged and positioned in said bodysuch that they very largely remove droplets from the water which passesbetween them so that the air which also passes between them issubstantially free of droplets, whereby maximum water quantities aremaintained on said tubes and scale formation is reduced, means tocirculate a fluid from which heat is to be extracted through said tubesand means providing an air passage from said enclosed means to a regionof' discharge.

2. An evaporative heat exchanger as claimed in claim 1 in which saidpumping means includes means to vary the rate of flow of the water tosaid injecting means.

3. An evaporative heat exchanger as claimed in claim 1 wherein thepermeable body is of substantially uniform thickness and the plane ofthe face of said body is disposed at an oblique angle to the axis of theconduit.

4. An evaporative heat exchanger as claimed in claim 1 wherein misteliminators are located in the air path between said tubes and theregion of air discharge.

5. An evaporative heat exchanger of the indirect heat exchange typecomprising means defining a conduit of rectangular cross section havingan air intake at one end exposed to atmosphere, a throat and a regionbeyond the throat discharging to atmosphere, said air intake throat andregion providing a generally horizontal passageway, means to injectwater into said throat in the form of a series of oval sectionintersecting sprays which fill said throat, thereby to pump ambient airinto the ,conduit at its intake end, the long axes of said sprays beingnormal to the long axis of the cross section of said conduit, means toreceive water issuing from said region, means to pump the water fromsaid water receiving means to said injection means, a plurality of tubesarranged in diagonally offset pairs which traverse the space between thewalls of the conduit to define a permeable rectangular body ofsubstantially uniform thickness to be impinged upon by said sprays, saidtubes being arranged and positioned in said body such that they verylargely remove droplets from the water which passes between the tubes sothat the air which also passes between is substantially free ofdroplets, means mounting said body between said throat and said waterreceiving means with the plane of the face of said body at an obliqueangle to the axis of said conduit and means to circulate a fluid fromwhich heat is to be ex-' tracted through said tubes.

6. An evaporative heat exchanger according to claim 5 wherein said,throat is of lesser cross sectional area than said air intake and saidregion beyond the throat. t

QERTEEAKCATE o1? teeiitmiow Patent No. 3 800,553 Dated April 2,1974

invent-CNS) JOHN ENGALITCHEFF, JR

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Title page, No. [73} "Airfoil" to read -Aircoil--;'

Column 6, lih 135, delete -"iners ect" and substitute "intersect":

lir 1es '45 and 46, delete "said common plane" and substitute theintersection of the sprays-- Signed and sealed this 10th day'ofSeptember 1974.

(SEAL) Attestz MCCOY M. GIBSON, JR. (3. MARSHALL DANN J AttestingOfficer Commissioner ,of Patents F (Tn-(M PC4050 (10-69) USCQMM'DC5375-P69 i 13.5. GOVERNMENT PRINTING OFFICE "SB O366-384,

1. An evaporative heat exchanger of the indirect type comprising meansdefining a conduit extending in a horizontal direction and having an airintake at one end exposed to the ambient, means to inject water in ahorizontal direction within the conduit in the form of a plurality ofsprays of sufficient divergence to contact the inner surface of theconduit and to inersect Each other within the conduit, thereby to pumpambient air into the conduit at its intake end, enclosed means toreceive the water issuing from the other end of said conduit, means topump the water from said water receiving means to said injecting means,a tube bank positioned in said conduit, said tube bank comprising aplurality of tubes arranged in diagonally offset pairs which traversethe space between the walls of the conduit thereby to form a permeablebody, said tube bank being positioned in the path of said water betweensaid common plane and said water receiving means, to be impinged upon bysaid water sprays, said tubes being arranged and positioned in said bodysuch that they very largely remove droplets from the water which passesbetween them so that the air which also passes between them issubstantially free of droplets, whereby maximum water quantities aremaintained on said tubes and scale formation is reduced, means tocirculate a fluid from which heat is to be extracted through said tubesand means providing an air passage from said enclosed means to a regionof discharge.
 2. An evaporative heat exchanger as claimed in claim 1 inwhich said pumping means includes means to vary the rate of flow of thewater to said injecting means.
 3. An evaporative heat exchanger asclaimed in claim 1 wherein the permeable body is of substantiallyuniform thickness and the plane of the face of said body is disposed atan oblique angle to the axis of the conduit.
 4. An evaporative heatexchanger as claimed in claim 1 wherein mist eliminators are located inthe air path between said tubes and the region of air discharge.
 5. Anevaporative heat exchanger of the indirect heat exchange type comprisingmeans defining a conduit of rectangular cross section having an airintake at one end exposed to atmosphere, a throat and a region beyondthe throat discharging to atmosphere, said air intake throat and regionproviding a generally horizontal passageway, means to inject water intosaid throat in the form of a series of oval section intersecting sprayswhich fill said throat, thereby to pump ambient air into the conduit atits intake end, the long axes of said sprays being normal to the longaxis of the cross section of said conduit, means to receive waterissuing from said region, means to pump the water from said waterreceiving means to said injection means, a plurality of tubes arrangedin diagonally offset pairs which traverse the space between the walls ofthe conduit to define a permeable rectangular body of substantiallyuniform thickness to be impinged upon by said sprays, said tubes beingarranged and positioned in said body such that they very largely removedroplets from the water which passes between the tubes so that the airwhich also passes between is substantially free of droplets, meansmounting said body between said throat and said water receiving meanswith the plane of the face of said body at an oblique angle to the axisof said conduit and means to circulate a fluid from which heat is to beextracted through said tubes.
 6. An evaporative heat exchanger accordingto claim 5 wherein said throat is of lesser cross sectional area thansaid air intake and said region beyond the throat.